Institute of Organic Chemistry and Biochemistry, Academy of Sciences, 16610 - Prague, Czech Republic.
Saponins belong to chemicals with non-specific but efficient regulating activity in the
plant - insect chemical interaction. Their ecological role is connected with their
miscellaneous physiological activities and often depends on the minute details in their
chemical structure or on their quantitative content. Their toxic effect in insects is mostly
manifested in digestive dysfunctions, or in reduced or arrested growth and development.
Our presentation summarizes results achieved during the elucidation of the mechanism of
activity of the leek active compound aginoside, isolated and identified in our previous work [1].
Aginoside, a spirostan saponin, appeared to be responsible for the ecdysis-disturbing activity
of the leek flowers, Allium porrum, during the larval stage of metamorphosis of
the insect specialist, leek moth Acrolepiopsis assectella [2]. Mechanism is based
on the interference of saponins with cholesterol, the precursor in biosynthesis of ecdysone.
To explain the difference between the activity of leek flower extract and corresponding
equivalent of the pure aginoside, we analyzed the leek active fraction and isolated two
additional minor saponins: 6-deoxyaginoside and alliporin. Their structural and activity
relations with aginoside and digitonin will be discussed.
[1] J. Harmatha, B. Mauchamp, C. Arnault, K. Slama: Biochem. Syst. Ecol.: 15, 113 (1987).
[2] C. Arnault, et al.: In "Insects-Plants", Junk Publishers, Dordrecht, p.249 (1987).
Supported by GACR, grant No. 203/98/0451.